1. Field of the Invention
The present invention relates to cutting line feeders for weed and grass trimmers. More specifically, the invention is a cutting line feeder wherein pulling an actuation lever while operating the weed trimmer moves corresponding flanges on the spool and spool housing into and out of alignment, so that the difference in centrifugal force and angular velocity feeds additional cutting line.
2. Description of Related Art
Weed and grass trimmers having a cutting wire spinning in a horizontal plane are commonly used to trim grass in locations where a lawnmower cannot reach or would be inconvenient. The cutting wires used with such weed trimmers are designed to minimize injury in the event a spinning wire comes in contact with a person. Such cutting wires frequently break and/or wear during use, necessitating a means for feeding additional wire.
Several inventors have proposed various means for feeding additional wire as the weed trimmer is in operation, thereby saving time. A common proposal has been a cutting head having a spool and housing which rotate incrementally with respect to each other when the ground is struck with the cutting head. However, this solution risks damaging the weed trimmer. No one within the knowledge of the present inventor has proposed a feed mechanism actuated by a lever near the handle of the weed trimmer, actuating either a cable or solenoid mechanism for causing a difference in centrifugal force and angular velocity between the spool and spool housing, thereby feeding additional wire.
U.S. Pat. No. 4,118,864, issued to Charles B. Pittinger, Sr. et al. on Oct. 10, 1978, describes an incremental feed means for a weed trimmer. The trimmer includes a worm pinion mounted coaxially on top of a hollow shaft, and a plurality of spools mounted on horizontal axes, with the spools having gears engaging the worm pinion. A friction bar is positioned so that it can engage the upper portion of the worm pinion. The wire passes from the spools, between the worm pinion and hollow shaft, and down the hollow shaft, with the friction between the pinion and hollow shaft securing the wire in place. Engaging the worm pinion with the friction bar prevents it from turning with the rest of the assembly, causing it to rise, releasing the wire, so that centrifugal force pulls additional wire out. When the worm gear reaches a height wherein the friction bar is adjacent to a reduced diameter portion, the friction bar can no longer engage the work gear, so it falls back into place and continues to rotate, stopping the dispensing of wire.
U.S. Pat. No. 4,136,446, issued to Dwight E. Tripp on Jan. 30, 1979, describes a vegetation cutter having a mechanical line feed. A button on the handle is depressed, pushing a brake plate against a control ring, which is in turn pressed against a brake plate. The control ring is thereby angularly displaced. The control ring is linked to a ratchet engaging the spool. The ratchet moves from a first position to a second position, allowing the spool to rotate incrementally, dispensing a measured amount of additional wire.
U.S. Pat. No. 4,211,004, issued to Donald M. Woods on Jul. 8, 1980, describes a weed cutter with a mechanical line feed. The spool includes a gear having a Maltese cross configuration. The actuator is a round member having a shoulder portion with two opposing convex surfaces and two opposing concave surfaces. A pair of opposing pins are outside the actuator. The convex portion engages the Maltese cross to prevent movement of the spool. Rotation of the actuator brings the concave portion adjacent to the Maltese cross, allowing space for movement, while simultaneously bringing a pin within a slot on the Maltese cross, rotating the spool.
U.S. Pat. No. 4,265,019, issued to Lauren G. Kilmer on May 5, 1981, describes a vegetation trimmer having a filament which twists and untwists as it moves within a horizontal plane, thereby presenting changing cutting surfaces to the vegetation, resulting in even wear.
U.S. Pat. No. 4,285,128, issued to John W. Schnell et al. on Aug. 25, 1981, describes a spool feed mechanism for a grass trimmer. The spool has a ratchet wheel on each end, with the teeth offset from each other. A U-shaped member alternately engages and disengages the ratchet wheels, allowing the centrifugal force of the spinning end of the wire to pull additional measured increments of wire from the spool.
U.S. Pat. No. 4,633,588, issued to Charles B. Pittinger, Jr., on Jan. 6, 1987, describes a bump-feed filament vegetation trimmer. Several methods of feeding the filament are described. In some embodiments, a spool and housing spin together, with the housing having a series of upper and lower internal flanges corresponding to a series of flanges on the spool. In one embodiment, bumping the spool on the ground drives the spool from the lower to the upper flanges, with the friction slowing the rotation of the spool, so that the spool and housing rotate with respect to each other until the spool engages the upper flanges. Removing the spool from contact with the ground allows a spring to push the spool back towards the lower flanges, causing another increment of rotation. Another embodiment includes a fork for pushing the housing towards the spool, again causing the upper and lower flanges to sequentially engage the spool, allowing an increment of wire to be dispensed. In a third embodiment, the driveshaft includes a plunger having a large diameter portion and smaller diameter portion pushes a pair of balls against the spool, so that the driveshaft thereby engages the spool. Upward pressure on the plunger causes the reduced diameter portion to move adjacent to the balls, thereby momentarily disengaging the spool and driveshaft.
U.S. Pat. No. 5,109,607, issued to Robert G. Everts on May 5, 1992, describes an automatic line trimmer head. An indexer cam on top of the spool includes a plurality of ramps along its outer edge, and a plurality of voids on its top surface. The ramps engage a plurality of followers on the inner surface of the housing. When sufficient wire is in use, the centrifugal force of the wire drives the indexer cam against the followers, causing it to move upwards where the voids engage a plurality of stop blocks. When the centrifugal force decreases due to wire breaking away, the indexer cam and spool travel downward within the housing, disengaging the indexer cam from the stop blocks, and allowing more wire to be dispensed.
U.S. Pat. No. 5,566,455, issued to Leonard Hagstrom on Oct. 22, 1996, describes a rotary filament vegetation trimmer with an air cooled filament. The head is shaped to form a centrifugal air pump, which rapidly increases the volume available for the air to provide refrigeration. The refrigerated air is directed towards bends in the wire, where the wire is most likely to fail.
U.S. Pat. No. 5,659,960, issued to Robert G. Everts et al. on Aug. 26, 1997, describes a line trimmer head having a ratchet to prevent spool rotation in the wrong direction during winding of wire around the spool.
U.S. Pat. No. 5,743,019, issued to Robert C. Berfield on Apr. 28, 1998, describes a line feed for a rotary wire trimmer. The line is wound around a large diameter spool, then a smaller diameter spool, then extends outward to form a cutting surface. When the end breaks off, centrifugal force causes additional wire to extend outward until equilibrium is reached.
U.S. Pat. No. 5,768,786, issued to Steven F. Kane et al. on Jun. 23, 1998, describes a brush cutting device having a handle which, when released, causes a brake to stop the rotation of the cutter and a cover to completely enclose the cutter.
German Pat. No. 2,832,649, published on Feb. 1, 1979, describes a mowing device having a wire which is fed by centrifugal force.
International Pat. App. No. WO 81/03106, published on Nov. 12, 1981, describes a vegetation cutter using an eccentric pivot to extend cutting line by centrifugal force as the cutting line shortens.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.